Pipes are used in numerous industries and pipelines are used to carry liquids, viscous materials, slurries, and steam from one location to the next. The pipes can have diameters ranging from an inch or less up to 144 inches or more. Over time, the pipe can become damaged or weakened. Repair of the pipe can involve shutting down the pipeline impacting operational activities and costs. It is known in the pipeline industry to repair the pipe while maintaining operations by installing half sole repair sleeves or split sleeves over the pipe. Once in place, the sleeves can be welded in place or a tightening or compression system can be used to hold the pipe halves together.
Especially in the case of larger diameter pipes, the sleeves are heavy and not easily manipulated. The first issue is getting the sleeve properly positioned in relation to the pipe to allow for the subsequent raising and alignment of the pipe and sleeve. The second issue is simply raising the sleeve which is heavy and cumbersome. The third issue is that once the sleeve is properly situated on the bottom half of the pipe and mated to the top half (or two sleeves each positioned along opposite sides of the pipe and mated), maintaining the positioning of the sleeve can be a challenge. Various methods are used in an attempt to hold the sleeves in position, including, but not limited to, pipe jacks, blocking, strapping, manual means, bracing, machine mounted platforms, etc.
Of the above methods, the use of pipe jacks is well known. An example of one common configuration of a pipe jack is custom made by Allan Edwards, Inc., of Tulsa, Okla., U.S.A. (depicted in FIG. 1). The pipe jack consists of a bracing support block that sits on top of the pipe to be repaired and a raising block that sits atop the bracing support block. A chain is affixed to one side of the raising block and removably attached on the other. A threaded rod is provided in the raising block so that rotation of the rod causes the raising block and bracing support block to separate thus tensioning the chain.
It is an accepted practice with known pipe jacks that the chain must circumferentially follow the pipe and that it must contact the pipe squarely. To achieve this, known pipe jacks are configured so that the ends of the chains, when connected to the lifting device, are coplanar. Thus, when attached, the chain that is looped around the pipe, the lifting head and the chain ends attached to the lifting mechanism are on the same axial plane with the axial plane perpendicular to the longitudinal axis of the pipe. This is intended to prevent twisting of the chain and undue forces on the pipe.
One problem with current pipe jacks is that rotation of the threaded rod results in side forces that can cause instability of the pipe jack. Another problem is that, as the tension on the chain increases, the force required to turn the rod is also increased. There is a propensity for the tightening wrench to slip off of the rod with the increasing force requirement, which can cause injury to the worker. Another problem is that pipe jacks of this type can be heavy and cumbersome to lift in place and to operate. A further problem is that rotation of the threaded rod is not ergonomically conducive.
In view of the shortcomings of known pipe jacks, there is a demand for a pipe jack which is simple to employ but capable of lifting and exerting distributed compression forces against the half sole repair sleeve to effectively position and install the sleeve. In addition, the pipe jack should be easy to use, be easy to manipulate, and remain stable as the half sole sleeves are secured in place.